This invention relates to heat exchangers, specifically tube-type heat exchangers made using tubes made from thermoplastic compositions, a major portion of which comprises certain types of partially aromatic polyamides or copolyamides, and a process to manufacture these heat exchangers.
Heat exchangers fabricated from metals are well known, and are used in a wide variety of automotive and other transportation vehicles, chemical processing, air conditioning, and refrigeration end-uses where there is a need to exchange heat between two fluid streams without bringing them into direct contact with each other. Metals have the advantage that they provide rapid conduction of heat through the wall, and generally posses high stiffness and strength properties. However, they are subject to corrosion from chemical attack. Engineering thermoplastics, especially polyamides, possess good chemical resistance and stiffness and strength properties at elevated temperatures. It is thus desirable to construct heat exchangers out of these thermoplastic materials.
Heat exchangers formed from thermoplastics, and methods for their manufacture are known. For example, U.S. Pat. Nos. 4,955,435; 5,469,915 and 5,499,676 disclose a number of panel heat exchangers formed from thermoplastics, preferable polyamides. U.S. Pat. Nos. 4,923,004 and 5,078,946 disclose a comfort heat exchanger made from a thermoplastic, preferably a polyamide, and a method to manufacture it.
Tube-Type Thermoplastic Heat Exchangers
The present invention relates to a tube-type exchanger formed from thermoplastics. These heat exchangers consist of structures where a multitude of tubes running lengthwise are arranged in a spaced apart manner and are integrally bonded to two manifolds at their ends. The manifolds are provided with a fluid inlet through which a first fluid enters and flows though the tubes, and a fluid outlet through which this first fluid exits. A second fluid flows around the tubes on their outside such that heat exchange is facilitated between the first and the second fluids across the wall of the tubes. Direct contact between the fluids is prevented by the tube walls and construction of the manifolds.
In cases where the second fluid requires containment, a thermoplastic shell may be provided that extends between the two manifolds enveloping the tubes and is in flow communication with the inlets and outlets for the second fluid. If the second fluid does not require containment, as in the case of ambient air, it is not necessary to provide a shell.